You can use Fotoxx on resource-strapped machines and the app can be navigated entirely with the keyboard.
I mage manipulation apps come in all shapes and sizes, but their list of features is usually inversely proportional to their usability. Fotoxx is a good exception. It offers a rich set of retouch and edit functions that go beyond merely changing brightness, contrast and colour, and yet it isn’t all that cumbersome to navigate.